U.S. patent application number 12/326567 was filed with the patent office on 2009-06-11 for semiconductor light-emitting device and method for manufacturing the same.
Invention is credited to Tsutomu Okubo.
Application Number | 20090146171 12/326567 |
Document ID | / |
Family ID | 40720697 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090146171 |
Kind Code |
A1 |
Okubo; Tsutomu |
June 11, 2009 |
SEMICONDUCTOR LIGHT-EMITTING DEVICE AND METHOD FOR MANUFACTURING
THE SAME
Abstract
A semiconductor light-emitting device and a method for
manufacturing the same can include a soft silicon resin
encapsulating an LED chip with a thin overcoat of microparticles
located on the silicon resin to prevent dirt and dust from
attaching to the silicon resin. The semiconductor light-emitting
device can include a base board having at least one LED chip, a
reflector fixed on the base board so as to enclose the LED chip, a
soft silicon resin having a tacky surface disposed in the
reflector, and an overcoat of microparticles on the silicon resin.
Thus, manufacturing lead time can be reduced because the
microparticles can attach to the silicon resin in a thin and single
layer and a solidifying process for an extra layer on top of the
silicon resin is not necessary. The overcoat of microparticles can
prevent dirt and dust from attaching to the silicon resin, and can
decrease optical variability in an inclined direction from an
optical axis of the device.
Inventors: |
Okubo; Tsutomu; (Tokyo,
JP) |
Correspondence
Address: |
CERMAK KENEALY VAIDYA & NAKAJIMA LLP
515 EAST BRADDOCK RD SUITE B
Alexandria
VA
22314
US
|
Family ID: |
40720697 |
Appl. No.: |
12/326567 |
Filed: |
December 2, 2008 |
Current U.S.
Class: |
257/98 ; 257/364;
257/E21.002; 257/E29.111; 257/E33.002; 438/29 |
Current CPC
Class: |
H01L 2933/0091 20130101;
H01L 2224/48247 20130101; H01L 2224/45144 20130101; H01L 2224/48091
20130101; H01L 33/56 20130101; H01L 33/44 20130101; H01L 2224/48091
20130101; H01L 2924/00014 20130101; H01L 2224/45144 20130101; H01L
2924/00 20130101 |
Class at
Publication: |
257/98 ; 438/29;
257/364; 257/E29.111; 257/E33.002; 257/E21.002 |
International
Class: |
H01L 21/02 20060101
H01L021/02; H01L 33/00 20060101 H01L033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 5, 2007 |
JP |
2007-314603 |
Claims
1. A semiconductor light-emitting device comprising: a base board
having at least one pair of electrodes configured to receive a
power supply; at least one LED chip located adjacent the at least
one pair of electrodes of the base board and including LED chip
electrodes, and each of the LED chip electrodes being electrically
connected to a respective electrode of the at least one pair of
electrodes of the base board; a reflector including a cavity, the
reflector being located adjacent the base board so as to enclose
the at least one LED chip; a silicon resin configured with a soft
silicon resin having a tacky surface, the silicon resin being
disposed in the cavity of the reflector and having an opposed
surface opposed to base board; and microparticles disposed on
substantially the entire opposed surface of the silicon resin so as
not to expose the silicon resin to an outside atmosphere.
2. A semiconductor light-emitting device comprising: a base board
having at least one pair of electrodes configured to be connected
to a power supply; at least one LED chip located adjacent the at
least one pair of electrodes of the base board, the LED chip
including electrodes electrically connected to the at least one
pair of electrodes of the base board; a silicon resin configured
with a soft silicon resin having a tacky surface, the silicon resin
being disposed above the at least one pair of electrodes of the
base board so as to encapsulate the at least one LED chip, and the
silicon resin including a surface opposed to the base board; and
microparticles disposed adjacent substantially the entire opposed
surface of the silicon resin that does not face the base board so
as not to expose the silicon resin to an outside atmosphere.
3. The semiconductor light-emitting device according to claim 1,
wherein the silicon resin includes at least one of a diffuser, a
phosphor material, colored particles using a dye, and a pigment,
and wherein the at least one of the phosphor material, colored
particles using a dye, and pigment are configured to selectively
absorb light having a predetermined wavelength.
4. The semiconductor light-emitting device according to claim 2,
wherein the silicon resin includes at least one of a diffuser, a
phosphor material, colored particles using a dye, and a pigment,
and wherein the at least one of the phosphor material, colored
particles using a dye, and pigment are configured to selectively
absorb light having a predetermined wavelength.
5. The semiconductor light-emitting device according to claim 1,
wherein the microparticles include SiO.sub.2.
6. The semiconductor light-emitting device according to claim 2,
wherein the microparticles include SiO.sub.2.
7. The semiconductor light-emitting device according to claim 3,
wherein the microparticles include SiO.sub.2.
8. The semiconductor light-emitting device according to claim 4,
wherein the microparticles include SiO.sub.2.
9. The semiconductor light-emitting device according to claim 1,
wherein the microparticles include at least one of a particle of
pigment, a particle of phosphor material, and a colored particle
using a dye.
10. The semiconductor light-emitting device according to claim 2,
wherein the microparticles include at least one of a particle of
pigment, a particle of phosphor material, and a colored particle
using a dye.
11. The semiconductor light-emitting device according to claim 3,
wherein the microparticles include at least one of a particle of
pigment, a particle of phosphor material, and a colored particle
using a dye.
12. The semiconductor light-emitting device according to claim 4,
wherein the microparticles include at least one of a particle of
pigment, a particle of phosphor material, and a colored particle
using a dye.
13. The semiconductor light-emitting device according to claim 5,
wherein the microparticles include at least one of a particle of
pigment, a particle of phosphor material, and a colored particle
using a dye.
14. The semiconductor light-emitting device according to claim 6,
wherein the microparticles include at least one of a particle of
pigment, a particle of phosphor material, and a colored particle
using a dye.
15. A method for manufacturing a semiconductor light-emitting
device comprising: providing a base board that includes at least
one pair of electrodes and at least one LED chip electrically
connected to the at least one pair of electrodes; encapsulating the
at least one LED chip with a silicon resin having a tacky surface
exposed to an outside atmosphere; solidifying the silicon resin;
and placing microparticles on substantially the entire tacky
surface of the silicon resin such that the tacky surface of the
silicon resin is not exposed to the outside atmosphere.
16. The method for manufacturing a semiconductor light-emitting
device according to claim 15, wherein the silicon resin includes at
least one of a diffuser, a phosphor material, and a pigment
configured to selectively absorb light having a predetermined
wavelength.
17. The method for manufacturing a semiconductor light-emitting
device according to claim 15, wherein the microparticles include at
least one of a particle of pigment, a particle of phosphor
material, and a colored particle using a dye.
18. The method for manufacturing a semiconductor light-emitting
device according to claim 16, wherein the microparticles include at
least one of a particle of pigment, a particle of phosphor
material, and a colored particle using a dye.
19. The method for manufacturing a semiconductor light-emitting
device according to claim 15, wherein placing microparticles
includes spraying microparticles onto the tacky surface of the
silicon resin.
20. The method for manufacturing a semiconductor light-emitting
device according to claim 15, wherein the microparticles include
SiO.sub.2.
21. The semiconductor light-emitting device according to claim 1,
wherein the microparticles, reflector, base board, and base board
electrodes encapsulate the entire silicon resin such that no
surface of the silicon resin is exposed to outside atmosphere.
22. The semiconductor light-emitting device according to claim 2,
wherein the microparticles, base board, and base board electrodes
encapsulate the entire silicon resin such that no surface of the
silicon resin is exposed to outside atmosphere.
23. The semiconductor light-emitting device according to claim 2,
wherein the microparticles are disposed in a dome shape on the
silicon resin.
24. The semiconductor light-emitting device according to claim 1,
wherein the reflector is formed in a substantially tubular shape.
Description
[0001] This application claims the priority benefit under 35 U.S.C.
.sctn.119 of Japanese Patent Application No. 2007-314603 filed on
Dec. 5, 2007, which is hereby incorporated in its entirety by
reference.
BACKGROUND
[0002] 1. Field
[0003] The presently disclosed subject matter relates to
semiconductor light-emitting devices including an LED chip and to a
manufacturing method for the same, and more particularly to
reliable semiconductor light-emitting devices including a silicon
resin for encapsulating the LED chip and to the manufacturing
method for these devices.
[0004] 2. Description of the Related Art
[0005] Various semiconductor light-emitting devices including an
LED chip have been used for general lighting in recent years. One
reason is that an LED chip may be a favorable light source with
respect to energy savings and environmental concerns. In addition,
semiconductor light-emitting devices including an LED chip can emit
variously-colored light while the structure thereof can be thin and
small in size. High power LED chips have been developed and have
been used as a light source in keeping the above trend.
[0006] However, while high power LED chips have been used as a
light source for light-emitting devices, an epoxy resin that has
been generally used as an encapsulating resin for LEDs has become
difficult to use for semiconductor light-emitting devices,
especially for devices that require high reliability. This is
sometimes due to stress caused by a difference of thermal expansion
coefficients between the material for mounting the LED chip and the
encapsulating resin that is composed of epoxy. In some cases, a
semiconductor light-emitting device that includes the epoxy resin
may be damaged by the above-referenced stress. In addition, an
epoxy resin may deteriorate in terms of quality and function
thereof due to ultraviolet rays emitted from an LED chip,
especially from the high power LED chip that can emit a light of
high intensity.
[0007] Thus, while high-power LED chips become more prevalently
used as a light source for a semiconductor light-emitting device, a
soft silicon resin has been more frequently employed as an
encapsulating resin in these devices. A characteristic of the soft
silicon resin is that it may not be damaged by the above-described
stress and may not deteriorate in quality due to ultraviolet rays.
A soft silicon resin can generally resolve or reduce the problems
caused by the ultraviolet rays and the stress. However, certain
other problems or concerns are present when using a soft silicon
resin, such as the characteristic that dirt and dust may easily
attach to a surface thereof during the manufacturing process for
the light-emitting device. Dirt and dust and other debris are
attracted to the silicon resin because the surface thereof might be
tacky.
[0008] A conventional light-emitting device that may resolve the
above-described problems, for example, is disclosed in Patent
Document No. 1 (Japanese Patent Application Laid Open
JP2007-036030). According to Patent Document No. 1, and as shown in
FIG. 6, a pair of lead frames 23a, 23b is insert-formed in a casing
21 that includes a cavity 22 for encapsulating an LED chip 24 with
encapsulating resins described later. The pair of lead frames 23a,
23b is depicted on a bottom surface of the cavity 22.
[0009] The LED chip 24 is mounted on the lead frame 23a via a
conductive material and has one electrode thereof that is
electrically connected to the lead frame 23a via one bonding wire
25a. The other electrode of the LED chip 24 is electrically
connected to the lead frame 23b via the other bonding wire 25b. A
first silicon resin 26a including a phosphor 28 is disposed in the
cavity 22 so as to encapsulate the LED chip 24.
[0010] The phosphor 28 can absorb light emitted from the LED chip
24 and can convert the light into a different wavelength of light
as compared to that of the light emitted directly from the LED chip
24. Therefore, the light-emitting device including the LED chip 24
may emit variously-colored light according to the type, quality,
kind, etc., of phosphor 28 located within the resin 26a. The first
silicon resin 26a including the phosphor 28 may also protect the
LED chip 24 from problems caused by dust, moisture, etc.
[0011] In this case, dirt and dust may attach to a surface of the
first silicon resin 26a. Accordingly, the surface of the first
silicon resin 26a is covered by a second silicon resin 26b that is
configured with a hard silicon resin having a higher hardness as
compared to the first silicon resin 26a. Thus, the second silicon
resin 26b having a high hardness can prevent dirt and dust from
attaching to a surface thereof, and therefore the light-emitting
device can operate reliably and maintain predetermined optical
characteristics.
[0012] However, the above-described light-emitting device requires
a process for covering the surface of the first silicon resin 26a
with the second silicon resin 26b during manufacture. In addition,
the light-emitting device requires both a process for at least
partly solidifying the first silicon resin 26a before covering it
with the second silicon resin 26b and a process for solidifying the
second silicon resin 26b. Thus, a manufacturing method for the
light-emitting device may include certain problems or concerns,
such as increased lead time for manufacturing the device as
compared to that for manufacturing a conventional light-emitting
device.
[0013] In addition, the second silicon resin 26b may be difficult
to form in a thin and uniform layer in a short time with a simple
manufacturing machine. Thus, the light-emitting device may be
difficult to form in a thin manner while accomplishing
predetermined optical characteristics in line with the trend of
providing thinner devices. The conventional device may also include
variability in terms of optical characteristics from product to
product if a thickness of the second silicon resin 26b cannot be
made uniform in the overcoat and solidifying processes.
[0014] On the other hand, an inventor of the disclosed subject
matter discovered that a microparticle such as silicon dioxide and
the like can be useful as a luminescent material as disclosed in
Patent Document No. 2 (Japanese Patent Application Laid Open
JP2006-143861). A manufacturing method for the microparticle is
also disclosed in detail in Patent Document No. 2.
[0015] The above-referenced Patent Documents are listed below, and
are hereby incorporated with their English abstracts in their
entireties.
[0016] 1. Patent Document No. 1: Japanese Patent Application Laid
Open JP2007-036030
[0017] 2. Patent Document No. 2: Japanese Patent Application Laid
Open JP2006-143861
[0018] The disclosed subject matter has been devised to consider
the above and other problems, features, and characteristics. Thus,
embodiments of the disclosed subject matter can include
semiconductor light-emitting devices and associated manufacturing
methods that do not cause and/or are designed to prevent some of
the above-described problems, concerns, and characteristics related
to a thin and uniform overcoat and the manufacturing lead time,
etc. The disclosed subject matter can also include a light-emitting
device that is configured to decrease optical variability caused by
differences between a light-emitting color emitted from the optical
axis thereof and a light-emitting color emitted in an inclined
direction from the optical axis, and can reduce or change other
associated problems, features, and characteristics of the
conventional devices and methods.
SUMMARY
[0019] The presently disclosed subject matter has been devised in
view of the above and other problems, features, and
characteristics. Another aspect of the disclosed subject matter
includes methods of manufacture that provide various semiconductor
light-emitting devices including a thin and single layer overcoat
and which can provide less lead time while using a simple
manufacture machine with respect to conventional light-emitting
devices and processes.
[0020] According to an aspect of the disclosed subject matter, a
semiconductor light-emitting device can include: a base board
having at least one pair of electrodes that is connected to
electrode conductor patterns for receiving a power supply; at least
one LED chip mounted on the at least one pair of electrodes, and
also being electrically connected; a reflector being formed in a
substantially tubular shape, and fixed on the base board so as to
enclose the at least one LED chip; a soft silicon resin having a
tacky surface disposed in the reflector; and microparticles
configured to be disposed on substantially all the surface of
silicon resin opposite the base board so as not to expose the
silicon resin to the outside.
[0021] As a variation of the above-described exemplary
semiconductor light-emitting device, the reflector can be
eliminated. The semiconductor light-emitting device can include:
the base board; the at least one LED chip; the silicon resin
disposed on the pair of electrodes so as to encapsulate the at
least one LED chip and bonding wire(s); and microparticles
configured to be disposed in a dome-shape on substantially all the
surface of silicon resin that does not face the base board so as
not to expose the silicon resin to the outside.
[0022] In the above-described exemplary semiconductor
light-emitting device, the silicon resin can include at least one
of a diffuser, a phosphor material, colored particles using a dye,
and a pigment, wherein the phosphor material, colored particles
using a dye, and pigment are configured to selectively absorb light
having a predetermined wavelength. The microparticles can be
configured with SiO.sub.2, and also can include at least one of a
particle of pigment, a particle of phosphor material and a colored
particle using a dye.
[0023] According to the above-described exemplary semiconductor
light-emitting device, the device can reduce a decrease of light
intensity caused by dirt and dust attached on the light-emission
surface thereof because the silicon resin can be prevented from
accumulating dirt and dust thereon with the overcoat of
microparticles. In addition, because the microparticles can
accelerate mixing the light emitted from the LED chip with
wavelength-converted light via the phosphor material, the device
can reduce an optical variability that can otherwise be caused by
differences between a light-emitting color emitted from an optical
axis thereof and a light-emitting color emitted in an inclined
direction from the optical axis.
[0024] Another aspect of the disclosed subject matter includes a
method for manufacturing the above-described semiconductor
light-emitting devices that can include: preparing a base board
that includes at least one pair of electrodes, whereon at least one
LED chip is electrically connected; encapsulating the at least one
LED chip with a silicon resin having an tacky surface; solidifying
the silicon resin; and spraying microparticles on substantially all
surface of the silicon resin that does not expose to the
outside.
[0025] In the above-described exemplary method for manufacturing
the semiconductor light-emitting devices, the same or similar
variations of the device can be employed as set forth in paragraph
[0018].
[0026] According to the above-described exemplary method for
manufacturing semiconductor light-emitting devices, lead time can
be reduced with respect to a conventional manufacturing method
because the microparticles are not required to undergo a
solidifying process. Furthermore, because the microparticles can
attach to the silicon resin in a thin and single layer by spraying
them on the tacky surface of the silicon resin, the overcoat can be
formed in a short time with a simple manufacturing machine even if
the overcoat is not a flat surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] These and other characteristics and features of the
disclosed subject matter will become clear from the following
description with reference to the accompanying drawings,
wherein:
[0028] FIG. 1 is a cross-sectional summary view showing a structure
for a first exemplary embodiment of a semiconductor light-emitting
device made in accordance with principles of the disclosed subject
matter;
[0029] FIG. 2 is a cross-sectional summary view showing a structure
for a second exemplary embodiment of a semiconductor light-emitting
device made in accordance with principles of the disclosed subject
matter;
[0030] FIG. 3 is a cross-sectional summary view showing another
structure for the semiconductor light-emitting device shown in FIG.
1;
[0031] FIG. 4 is a cross-sectional summary view depicting a
manufacturing method for a semiconductor light-emitting device in
accordance with principles of the disclosed subject matter;
[0032] FIGS. 5A and B are diagrams showing a difference between an
embodiment of the disclosed subject matter and a comparative
example of a conventional semiconductor light-emitting device with
respect to each coordinate of an xy chromaticity diagram; and
[0033] FIG. 6 is a cross-sectional summary view depicting a
structure for a conventional semiconductor light-emitting
device.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0034] The first exemplary embodiment of the disclosed subject
matter will now be described in detail with reference to FIG. 1.
FIG. 1 is a cross-sectional summary view of a first exemplary
embodiment made in accordance with principles of the disclosed
subject matter.
[0035] The semiconductor light-emitting device can include: a base
board 2 having a pair of electrodes 3a, 3b exposed thereon; an LED
chip 4 that is mounted on one electrode 3a of the pair of
electrodes via a conductive material. The LED chip can include a
top and a bottom electrode connected to a respective one of the
pair of electrodes 3a, 3b via the conductive material and a bonding
wire 5, respectively. A reflector 1 can be formed in a
substantially tubular shape with a cavity, and disposed on the base
board so as to enclose the LED chip 4. A silicon resin 6 can be
disposed in the cavity formed by the reflector 1 and the base board
2.
[0036] In this embodiment, the silicon resin 6 can be configured as
a soft silicon resin having a tacky surface, and microparticles 7
such as SiO.sub.2 and the like can be attached to substantially the
entire surface of silicon resin opposite the base board 2 so as not
to expose the silicon resin 6 to the outside. Thus, the
light-emitting device can prevent dirt and dust from attaching to a
light-emission surface thereof that is composed of the
microparticle 7 formed on the silicon resin 6. Each of the
above-described components will now be described in detail.
[0037] The base board 2 can be made using high temperature
conductive materials, such as a metal board that is provided with
Au, Al, and the like with an insulating layer thereon or a ceramic
substrate, such as Al.sub.2O.sub.3, AlN, SiC, Si.sub.3N.sub.4 and
ZrO.sub.2. The base board 2 can be formed with the pair of
electrodes 3a, 3b on a surface thereof, and the pair of electrodes
3a, 3b can be connected to electrode conductor patterns for
receiving a power supply.
[0038] The reflector 1 can be composed of an opaque resin material,
metal material, ceramic material and the like, and can be fixed at
a predetermined position on the base board 2 via an adhesive
material with a high temperature conductivity, or the like. The
reflector 1 can define the cavity for exposing the pair of
electrodes 3a, 3b and can be configured for reflecting the light of
an LED chip 4. Thus, the reflector 1 can be made using high
reflectivity materials for the LED chip 4. Alternatively, an inner
surface of the reflector 1 can be coated with a material with high
reflectivity.
[0039] The reflector 1 can also be integrated with the base board 2
as one body. In the case when they are formed as one body, the base
board 2 including the reflector 1 can be insert-formed with the
pair of electrodes 3a, 3b using lead frames.
[0040] The LED chip 4 can include, for example, a blue LED chip
composed of a GaN-based compound semiconductor, a red LED chip
composed of GaAs-based compound semiconductor and the like for any
purpose or specific application. The LED chip 4 can be mounted on
the pair of electrodes 3a, 3b of the base board 2 in the cavity of
the reflector 1. The pair of electrodes 3a, 3b can be electrically
connected to both electrodes of the LED chip 4 via die bonding and
wire bonding, respectively.
[0041] When the LED chip 4 is mounted on one electrode 3a of the
pair of electrodes via die bonding, a solder, a silver paste and
the like can be used as an adhesive material that is electrically
conductive. When an electrode of the LED chip 4 is electrically
connected to the other electrode 3b of the pair of electrodes via
wire bonding, an Au wire and the like can be used as a conductive
wire 5. The LED chip 4 is not limited to one chip, and can also
include a plurality of chips. Additionally, the LED chip can be
mounted on the pair of electrodes via a sub mount.
[0042] The silicon resin 6 can be configured as a soft silicon
resin having a tacky surface. The soft silicon resin can be an
elastomeric resin and a gelled resin that have hardness within the
range of substantially 30 to 80 in shore hardness A. A
thermosetting silicon resin can also be used as the silicon resin
6. The silicon resin 6 can include a diffuser such as TiO.sub.2,
CaCO.sub.3 and the like for efficiently emitting light to the
outside.
[0043] Thus, the silicon resin 6 does not deteriorate very much in
quality and function due to ultraviolet rays in the light emitted
from the LED chip 4, and can efficiently emit the light emitted
from the LED chip 4 to the outside therethrough. In addition, the
light-emitting device is configured to prevent damage due to stress
caused by a difference of thermal expansion coefficients between
the silicon resin 6 and the above-described materials for mounting
the LED chip 4 because the silicon resin 6 can be configured as a
soft silicon resin that can absorb the stress.
[0044] The microparticles 7 can be configured in various shapes and
can include various materials such as phosphors. The microparticles
7 can be sized within a range of substantially 1 to 20 micrometer
in mean particle size. In this case, because the microparticles 7
can be dispersed in a volatile solution and can be sprayed on the
soft silicon resin, or because the microparticle 7 can be directly
splayed by air on the soft silicon resin, the overcoat process of
the microparticles 7 can be easier than a conventional process such
as when the soft silicon resin is covered with a harder silicon
resin, and also can be carried out by a simple manufacturing
machine even if a surface of the silicon resin 6 is not flat.
[0045] In addition, the thickness of the overcoat formed on the
silicon resin 6 can become thinner by using microparticles 7 that
have a mean particle size of less than 10 micrometer. The
microparticles 7 can include different materials, such as
SiO.sub.2, Al.sub.2O.sub.3, B.sub.2O.sub.3, MgO, CaO, ZnO, AlN,
TiO.sub.2, acrylic, polycarbonate and the like. For example,
SiO.sub.2 can be a favorable material in certain application and
can maintain a strong attachment to the silicon resin 6 while also
being a clear material having high transparence.
[0046] Furthermore, the microparticles 7 are not necessarily
transparent, and can be composed of a colored material such as red,
green and the like, that is, a pigment, a colored microparticle
using a dye and a phosphor for selectively absorbing light emitted
from the LED chip 4 and emitting a different colored light from
that of the LED chip 4. When both the above-described colored
microparticle and a mixture microparticle mixed with a transparent
material with a colored material can be used as the microparticles
7, the microparticles 7 can provide a color correction for a
colored light of the light-emitting device.
[0047] The microparticles 7 can attach to substantially the entire
surface of silicon resin opposite the base board 2 so as not to
expose the silicon resin 6 to the outside. The overcoat layer
formed on the soft silicon resin is not necessarily a plurality of
layers. For example, a single layer of microparticles can be formed
on the soft silicon resin. Thus, because the thickness of the
overcoat layer can be substantially the same thickness as the
particle size of the microparticle, the overcoat layer can be
formed as a thin single layer.
[0048] The reason that the microparticles 7 can attach to the soft
silicon resin which has a tacky surface, but do not attach to each
other is because the microparticles 7 can be formed of an
incohesive material. Therefore, even when the microparticles may
accumulate on the surface of the soft resin 6, the single layer can
be easily formed by blowing the excess microparticles 7 away with
an air gun, etc.
[0049] A second exemplary embodiment of the disclosed subject
matter will now be described with reference to FIG. 2. A
semiconductor light-emitting device of the second exemplary
embodiment is shown in FIG. 2, wherein the same or similar elements
shown in FIG. 1 are referenced by same reference numerals. The
light-emitting device can be similar to the light-emitting device
shown in FIG. 1. A difference between the semiconductor
light-emitting devices of FIG. 1 and FIG. 2 can be the absence of a
reflector structure in the embodiment shown in FIG. 2.
[0050] In the second exemplary embodiment, a circuit board that is
generally used for a surface mount device can also be used as the
base board 2 similar to the first exemplary embodiment. When the
silicon resin 6 is disposed on the base board 2, the soft silicon
resin can be directly disposed by a dispenser so as to encapsulate
the LED chip 4 mounted on the pair of electrode 3a, 3b.
[0051] In this case, the shape of the silicon resin 6 can be formed
using the variables of quantity, hardness and surface tension of
the soft silicon resin to obtain a desired form. Therefore, because
the process may be simple and can be carried out in a short time by
a simple manufacturing machine, the process may be useful for use
in manufacturing the above-described surface mount LED devices that
are thin and small and are produced at low cost. However, the
method may make it difficult to exactly form a same and consistent
shape in many products.
[0052] When it is desired that the silicon resin 6 form a same and
consistent shape in many products, a molding tool can be placed on
the base board 2 and used to accurately and consistently dispose
and shape the silicon resin 6. When the silicon resin 6 is disposed
in the cavity formed by the molding tool and the molding tool is
removed after the silicon resin 6 is solidified, the silicon resin
6 can be formed in an exactly same shape consistently for many
products in accordance with the cavity of the molding tool.
[0053] After the silicon resin 6 is formed, the above-described
microparticles 7 can be splayed on the soft silicon resin or the
soft silicon resin on the base board 2 can dipped into a bath of
microparticles 7. Thus, a single layer of microparticles 7 can be
formed in a dome-shape on the entire surface of soft silicon resin
6 that does not face the base board 2 so as not to expose the
silicon resin 6 to the outside. The microparticles 7 can also be
softly blown with an air gun or the like, such that the overcoat
layer can be perfectly formed in a thin single layer because excess
microparticles 7 can be removed. Thus, the light-emitting device of
the second exemplary embodiment can emit a wide range of light on
the base board 2.
[0054] Another exemplary embodiment of the disclosed subject matter
will now be described with reference to FIG. 3. FIG. 3 shows a
semiconductor light-emitting device that can be configured similar
to the semiconductor light-emitting device shown in FIG. 1. Thus,
the same or similar elements in FIG. 3 are referenced using the
same reference numerals as those in FIG. 1. A difference between
the semiconductor light-emitting devices of FIG. 1 and FIG. 3 can
be the inclusion of a phosphor 8 in the device shown in FIG. 3.
[0055] The phosphor 8 can absorb a predetermined wavelength of
light emitted from the LED chip 4, and can emit a different
wavelength of light from that emitted from the LED chip 4. For
example, when the LED chip is a blue LED chip that emits a blue
light with a peak wavelength of 450 nm, YAG: Ce, (Ca, Sr,
Ba).sub.2SiO.sub.4: Eu, and the like can be used as the phosphor
8.
[0056] The phosphor 8 can be mixed with the silicon resin 6, and
the silicon resin 6 can be disposed along with the phosphor 8 in
the cavity of the reflector 1. When the LED chip 4 is provided with
a power supply via the pair of electrodes 3a, 3b, the
light-emitting device can emit a mixture light that includes light
emitted from the LED chip 3 mixed with wavelength-converted light
emitted via the phosphor 8. Alternatively, the light-emitting
device can be configured to emit only the wavelength-converted
light using the LED chip 4 and the phosphor 8. The silicon resin 6
can also include a pigment that can absorb light having a
predetermined wavelength.
[0057] The above-described structure can include an overcoat of
microparticles 7 on the silicon resin 6 as described in the first
and second exemplary embodiments. Therefore, the light-emitting
device can also prevent dirt and dust from attaching to the
light-emission surface thereof. In addition, the microparticles 7
can accelerate the mixture of light emitted from the LED chip 4
with light that is wavelength-converted light emitted via the
phosphor 8.
[0058] As described above, conventional light-emitting devices
including both an LED chip and a phosphor may exhibit a problem or
feature such as optical variability that is caused by a difference
between light-emitting color of light emitted from the optical axis
thereof and light-emitting color of light emitted in an inclined
direction from the optical axis. However, the microparticles 7 can
reduce the optical variability because the microparticles 7 can
accelerate mixing of light emitted from the LED chip 4 with
wavelength-converted light emitted via the phosphor material 8.
[0059] A manufacturing method for the above-described semiconductor
devices will now be described in detail with reference to FIGS.
4A-D. The same or similar elements in FIGS. 4A-D are used to
reference the same or similar features as shown in FIGS. 1-3.
[0060] In process A shown in FIG. 4(A), an exemplary method for
manufacturing semiconductor light-emitting devices can include:
preparing or providing a base board 2 that includes at least one
pair of electrodes 3a, 3b, whereon at least one LED chip 4 is
mounted and is electrically connected; fixing a reflector 1 to the
base board, the reflector being formed in a substantially tubular
shape with a cavity so as to enclose the at least one LED chip 4
therein. In this case, the LED chip 4 can be electrically connected
using a flip chip via die bonding and wire bonding.
[0061] In process B shown in FIG. 4(B), the method can include
filling a silicon resin 6 in the cavity using a dispenser 9 so as
to enclose the at least one LED chip 4 mounted on the at least one
pair of electrodes 3a, 3b of the base board 2.
[0062] In process C shown in FIG. 4(C), the method can include
solidifying the silicon resin 6. In this case, for instance, the
silicon resin 6 can be solidified for four hours at 150 degrees
centigrade. However, it should be noted that the surface of the
silicon resin 6 can be solidified either before process D
(described below), and/or the silicon resin 6 can be absolutely
solidified after process D.
[0063] In process D shown in FIG. 4(D), the method can include
spraying the microparticles 7 on the silicon resin 6 using a
sprayer 10. In this case, the microparticles 7 are dispersed in a
volatile solution and can be sprayed on the silicon resin 6.
Moreover, the microparticles 7 can be directly sprayed by the
sprayer 10 onto the resin 6. If excess microparticles 7 are
attached to or stacked on the silicon resin 6, the overcoat layer
can be formed as a thin and single layer by blowing the
microparticles 7 with an air gun and/or the like.
[0064] According to the above-described manufacturing method, a
hard silicon resin is not required to be disposed on the surface of
silicon resin 6. Therefore, both resins can be solidified at the
same or different times with respect to each other. Thus, the
manufacturing method can provide various semiconductor
light-emitting devices in less lead time with respect to a
conventional device. Furthermore, the method can form a thin and
single overcoat layer on the silicon resin 6 in a short time and
with a simple manufacturing machine even if the surface of the
silicon resin 6 is not flat.
[0065] Results of an exemplary experiment using a semiconductor
light-emitting device made in accordance with principles of the
disclosed subject matter as compared to a comparative device are
described as follows.
COMPARATIVE EXAMPLE
[0066] A comparative example device includes: a base board 2
comprising a glass epoxy board; a reflector 1 configured of a
resin; a blue LED chip 4 having a dominant wavelength of 455-460 nm
mounted on a pair of electrodes and electrically connected to a
power source; and a soft silicon resin 6 having 45 in shore
hardness A disposed in a cavity of the reflector 1.
Embodiment
[0067] An embodiment device further includes microparticles 7 of
SiO.sub.2 having a mean particle size of 4 to 8 micrometer and
located on the soft silicon resin 6 of the comparative example. In
this case, the microparticles 7 extend on substantially the entire
surface of the silicon resin 6 by application of a brush, and
excess microparticles 7 are blown off with an air gun.
[0068] Results of a sticking test will now be given with respect to
the embodiment and the comparative example. When a plastic sheet is
pressed to the comparative example, the plastic sheet easily
attaches to the silicon resin 6 of the comparative example.
However, the plastic sheet does not attach to the surface of the
embodiment device when the plastic sheet is pressed to the
embodiment.
[0069] Results of light intensity measurements can be described as
follows. When a light intensity of the comparative example device
is based on 100, a light intensity of the embodiment device is 96.
Thus, the microparticles 7 of the embodiment device do not
practically affect the light intensity of the embodiment
light-emitting device.
[0070] Results of directional characteristics with respect to
chromaticity using a goniometer will now be described with
reference to FIGS. 5A-B. The vertical axis shown in FIG. 5(A) shows
the x-axis in a CIE xy chromaticity diagram, and the vertical axis
shown in FIG. 5(B) shows the y-axis in the CIE xy chromaticity
diagram. The horizontal axes shown in FIGS. 5(A) and (B) show an
inclined angle based on an optical axis (0 degree) of the
semiconductor light-emitting device. For example, the optical axis
for the devices shown in FIGS. 1-4D and 6 is a vertical line
extending from a center of each of the LED chips (4, 24).
[0071] For instance, when the horizontal axes are 40 degrees, each
of the vertical axes show chromaticity of light emitted in the
inclined direction of 40 degrees from the optical axis of the
device. The embodiment device exhibits smaller chromaticity
variation than that of the comparative example. Thus, the disclosed
subject matter can decrease optical variability that is caused
between a difference in light-emitting color emitted from the
optical axis and light-emitting color emitted in an inclined
direction from the optical axis.
[0072] In addition, when the semiconductor light-emitting device is
mounted on a circuit board at a peak temperature of 260 degrees
centigrade in a reflow soldering process, the microparticles 7 and
the silicon resin 6 prevent problems such as peeling and the
like.
[0073] Thus, the disclosed subject matter can provide a
semiconductor light-emitting device with high reliability that can
reduce the optical variability caused between a difference in
light-emitting color emitted from the optical axis thereof and
light emitting color emitted in an inclined direction from the
optical axis. In addition, a method for manufacturing a
semiconductor light-emitting device in accordance with principles
of the disclosed subject matter can reduce lead time with respect
to that of a conventional manufacturing method because the
microparticles 7 do not require a process for solidification.
[0074] While there has been described what are at present
considered to be exemplary embodiments of the invention, it will be
understood that various modifications may be made thereto, and it
is intended that the appended claims cover such modifications as
fall within the true spirit and scope of the invention. All
conventional art references described above are herein incorporated
in their entirety by reference.
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